The present invention relates to actuator apparatus, in particular for an aircraft flight control.
A particularly advantageous application of the invention lies in actuating an element for adjusting a tail plane on an airplane (pitch control), but other applications are also possible.
In certain airplanes, pitch control surfaces are actuated, as shown in FIG. 1, by means of two main drive systems 1 and 2, and by means of a differential 3 which connects outlet shafts 4, 5 from said two systems to a control shaft 6 connected to a pitch control surface 10.
In general, these two systems 1 and 2 are hydraulic systems. Each of them comprises a hydraulic motor 7 actuated by a hydraulic source 8, together with brake-forming means 9 which enable the shaft of said motor 7 to be locked whenever the hydraulic pressure in the corresponding system becomes low, so as to define a bearing point for the differential 3 and allow the second hydraulic system on its own to drive the differential 3 and the control shaft 6 connected to the pitch control surface 10.
It is desirable to make actuator devices even safer so as to minimize risk in the event of breakdown.
Objects of the invention are to propose a solution for this purpose that is both simple and particularly reliable.
To this end, the invention provides actuator apparatus, in particular for an airplane flight control, the device comprising at least two main drive systems and a differential which connects outlet shafts from the two systems to a control shaft connected to an element to be actuated and also including means for locking each outlet shaft of the drive systems when the system for driving it is not operating; the apparatus including at least one auxiliary drive motor and a clutch mechanism mounted on the outlet shaft of one of the main systems and suitable for automatically driving said outlet shaft by means of the auxiliary motor when the corresponding main drive system is not operating and for automatically locking said outlet shaft when said main drive system and said auxiliary motor are not operating.
In a particularly advantageous variant, the clutch mechanism comprises:
an intermediate rotor mounted to rotate on the outlet shaft;
first friction means interposed between said intermediate rotor and a portion secured to the outlet shaft, said first friction means, when in engagement, uniting said intermediate rotor and said outlet shaft;
second friction means interposed between said intermediate rotor and a casing of the mechanism, said second friction means, when in engagement, uniting said intermediate rotor and said casing;
spring means suitable for exerting a force on a portion secured to the outlet shaft, said force tending firstly to put the first friction means into engagement and secondly, when said means are in engagement, to exert an axial force on the intermediate rotor tending to put the second friction means into engagement;
means which oppose the force exerted by the spring means so long as the main drive system for the outlet shaft is in operation; and
a cam and cam follower means interposed between said intermediate rotor and a rotor which is mounted to rotate on the outlet shaft and which is driven by the auxiliary motor, said cam and said cam follower means being such that when the auxiliary motor is in operation while the main drive system is not in operation, they push the intermediate rotor axially back into a position where the second friction means are no longer in engagement and in which said intermediate rotor is driven.
It will be observed that such a structure makes it possible to declutch the auxiliary motor automatically as soon as the motor ceases to turn or the main system on which it is mounted is in operation.
It makes it possible to lock the outlet shaft of the main system and the outlet of the auxiliary motor when neither said auxiliary motor nor said main system is operating.
A particularly advantageous application of the invention lies in the case where the main drive systems are of the hydraulic type and where the auxiliary drive motor is of the electrical type.
In which case, it is preferable for the means which oppose the force exerted by the spring means so long as the main drive system of the outlet shaft are in operation, to be of the hydraulic piston type with the force exerted by said piston being a function of the pressure in said main drive system.
In other variant embodiments, these means can be of the solenoid type.